PRACTICAL APPLICATIONS 299 



two hours, and if the reaction is positive, a whitish ring makes its appear- 

 ance at the point of contact of the two serums, the controls remaining 

 negative. According to Citron, this ring test is also evident in the pres- 

 ence of scarlet fever, measles, and syphilis. 



FLOCCULE-FORMING REACTIONS 



Fornet Ring Test. Owing to the wonderful activity that has marked 

 the research work of syphilis several precipitation tests for diagnostic 

 purposes were devised. These have all been overshadowed and forsaken 

 for the Wassermann complement-fixation test. Fornet applied his ring 

 test, using the serum of patients with manifest luetic symptoms as the 

 precipitinogen, and the serum of paretics as the precipitating or immune 

 serum. Klausner advocated a simple test consisting of mixing in a small 

 test-tube 0.2 c.c. of fresh, active, and absolutely clear serum, with 0.6 

 c.c. of distilled water. This serum and the control mixtures are allowed 

 to stand at room temperature for from seven to fifteen hours, when a 

 thick, flocculent precipitate of fibrin globulin will appear at the bottom 

 of the tube. 



Porges-Meier Reaction. Forges and Meier observed that luetic 

 serums are capable of producing flocculent precipitates from solutions 

 of lecithin and similar salts. Two-tenths of a cubic centimeter of a 1 

 per cent, solution of Merck's sodium glycocholate in distilled water is 

 placed in narrow test-tubes, and an equal amount of the patient's 

 serum, which must be absolutely clear and inactivated by heating at 

 56 C. for thirty minutes, is added. This mixture and the known nor- 

 mal and luetic controls are kept at room temperature for from eighteen 

 to twenty-four hours. A positive reaction is marked by the appearance 

 of distinct coarse flocculi, mere turbidity or faint precipitation being 

 regarded as negative. 



Herman-Perutz Reaction. More recently Herman and Perutz have 

 devised a similar test requiring the following two solutions : Solution 1 

 (stock solution, diluted 1: 20 with distilled water before use) consists of: 

 Sodium glycocholate, 2 gm., cholesterol, 0.4 gm.; 95 per cent, alcohol, 

 100 c.c. Solution 2 (freshly prepared before use) is a 2 per cent, solu- 

 tion of sodium glycocholate in distilled water. The test is performed by 

 adding to 0.4 c.c. of clear inactive serum (heated at 56 C. for half an 

 hour) in a small test-tube 0.2 c.c. of solution 1 and 0.2 c.c. of solution 2. 

 The tubes are tightly plugged with cotton and set aside at room tem- 

 perature for twenty-four hours, after which the presence or absence of 

 precipitation is noted. It is well'in this test, as in all immunologic re- 



